Turbine-blade fastening.



G. ROTH.

TURBINE BLADE FASTENING.

APPLICATION FILED APR. 16, 1908.

Patented Nov. 3, 1908.

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U. ROTH.

TURBINE BLADE FASTENING.

APPLICATION FILED APB..16,.190B.

902,91 5,, Patented Nov. 3, 1908.

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fix Z zzza CARL ROTH, OF ZEHLENDOBF, NEAR BERLIN, GERMANY.

TURBINE-BLADE FASTENING.

Specification of Letters Patent.

Application filed April 16, 1908.

Patented Nov. 3, 1908.

Serial No. 427,396.

T 0 all whom it may concern:

Be it known that I, CARL Born, a citizen of the Confederation of Switzerland, and resident of 9 Annastrasse, Zehlendorf, near Berlin, Kingdom of Prussia, German Empire, have invented certain new and useful improvements in T urbine-Blade Fastenings, of which the following is an exact specification.

This invention relates to the fastening of turbine blades in the drums and casings of turbines. In such blade fastenings, blade carrying rings have been fixed in the grooves in the turbine drum and casings and it hasalso been proposed to effect the holding by means of divided holding rings placed in the grooves and fastened therein by means of a calking ring. Such constructions do not simultaneously utilize the whole gripping surface of the holding ring and provide an attachment sufficiently and equally strong at all points to resist the centrifugal force to which the blades in the moving drum are subjected.

The object of the present invention is to provide an improved construction of blade fastening for turbines which shall unite the advantages of easy construction, exact alinement of the blades, uniform and adequate strength over the whole blade root for resisting the centrifugal force and complete utilization of the gripping surface of the holding ring.

The invention consists in a blade fastening in which the blade root is formed by pressing, stamping or otherwise forming the edges into a suitable cross section-say rectangular or angle iron formwhich root is passed through grooves extending through the whole depth of the holding ring While said holding ring or rings is or are grooved on the under side to receive feet on the ends of the roots; the holding ring is of course inserted in the groove of the turbine drum or casing as the case may be and held in place in the known manner by means of a special calking ring.

The invention is illustrated in various modifications in the accompanying drawings, in which:

Figure 1 is a plan view of the blades holding ring and calking strip arranged according to this invention. Fig. 2 is a sectional view, illustrating the arrangement of the blade root and holding rings, the section being taken in a vertical plane. Fig. 2 is a section on the line AB in Fig. 2. Fig. 3 is a perspective view illustrating the method of assembling the holding rings and blades. Fig. & is a detached view of a single blade. Fig. 5 is a view similar to Fig. 1 illustrating a modified form of gripping groove in the holding ring. Fig. 6 is a view similar to Fig. 1 illustrating a further modified arrangement of the holding groove as employed with a blade of a different type. Fig. 7 is a vertical section of the arrangement illustrated in Fig. 6. Fig. 7 is a section on the line CD of Fig. 7. Fig. 8 is a detached view of the blade employed in the form illustrated in Figs. 6 and 7 Fig. 9 is a cross section through a modified form employing a taper blade root. Fig. 10 is a ver tical cross section through a modified form of blade holding arrangement according to the present invention. Fig. 11 is a cross section through a modified form of holding ring, the blade in this case is not illustrated in position. Fig. 12 is a section on the line E-F of Fig. 11. Fig. 13 is a vertical section through a further modified form of blade fixing device according to this invention. Fig. 14 is a section on the lines GI-I of Fig. 13. Fig. 15 illustrates another modified form of blade fixing according to this invention, and Fig. 16 is a section on the line JK of Fig. 15.

In the form shown in Figs. 1 to 44: the blade is pressed stamped or otherwise formed with a root of the form shown in plane in Fig. 2, that is to say, in the form of an angle iron with an extremely obtuse angle. The blade section a and the root section .7) are substantially equal in cross section and at the end of the root there is formed a foot 0 by bending, staving or otherwise upsetting the end of the root. The blades so formed are inserted in a divided holding ring, the parts d and c of Which are provided with vertical slots adapted to receive the inclined faces of the root 5.

The method of assembling the blades and holding rings will be clearly seen from Fig. 3, the blades 64 are first inserted in the ring part (Z, after which the ring part c is pushed over the root, so that the two ring parts come close together as illustrated in Fig. 1. The undersides of the ring parts (Z and e are grooved so as to admit the feet 0 on the ends of the blade roots. Thus in Fig. 2 it will be seen that the foot 0 on the blade root projects into the space between the holding grooves on the ring parts. The blade root however does not project below the holding ring parts (Z and e as can be clearly seen in Fi 2. After the blades and holding ring parts d and e are assembled as described and brought into the form illustrated in Fig. 1, the blades ring so formed is inserted into the groove in the turbine drum or casing f and a calking ring 9 is inserted in the groove and the ring and blades held in place by calking the ring 9. It will be seen that according to this form of blade fixing the foot 0 extends over the whole breadth of the root 6 and the root 1) is of substantially the same cross section as the blade itself. Further the whole depth of the holding ring is employed as a gripping surface for the blade roots. In this way the blades are easily assembled in place and are firmly held in correct alinement, while at the same time by providing the foot 0 over the whole breadth of the root a very strong and adequate resistance is offered to the centrifugal force to which the blades in the rotating drum are subjected.

According to the form of this invention illustrated in Fig. 5 instead of forming the blade root Z) of the obtuse angular cross section illustrated in Fig. 2 the blade root is formed in the shape of a parallelogram. Otherwise the construction in this form resembles that already described with refence to Figs. 1 to 4.

In the form illustrated in Figs. 6 to 8 I have shown this invention applied to the fixing of a somewhat modified form of blade. In this case the blade root 6 is of rectangular cross section and the grooves in the holding ring parts (Z and c are arranged at right angles to the contacting faces of these rings. Further in this form I have illustrated the foot 0 as extending on both sides of the root 6. Otherwise the arrangement of the blades holding ring and calking ring are similar to that already described with reference to Figs. 1 to 4 and the same remarks regarding the operation apply to both forms.

In the forms above described and illustrated the blade root 6 is arranged parallel in its length. I may however as illustrated in Fig. 9 arrange the blade root 5 with a taper and the foot 0 may be provided with inclined upper surfaces 0. In this form when the calking ring 9 is inserted and calked in place the foot 0 is pressed tightly against the bottom of the groove and an extremely rigid fixing is obtained.

It will be seen that with the construction of blade root illustrated in the figures that a cut-away-part 7a is formed on the blades and this may in some cases be disadvantageous. In order to avoid any evil effects from these chamfered parts I may provide a deepened groove in the turbine drum or casing f as shown in Fig. 10, so that the chamfered off part is is sunk within the groove of the turbine. In Fig. 10 I have also illustrated in a somewhat exaggerated degree of course, the tapering of the blade root 5 in the oppo site direction to that illustrated in Fig. 9. I 1 1 order to hold the two ring parts d and 6 together in a secure manner I may arrange a rib m on one of the ring parts (Z to engage in a recess on the other ring part c as shown in Figs. 11 and 12.

In all the forms already described the holding ring has been arranged in two parts engaging the blade root from opposite sides. I may however as illustrated in Figs. 13 and 14 arrange the holding ring in one part. In Figs. 13 and 14 the holding ring 12 engages the roots 6 from one side, so that the side of the ring from which the blade roots are entered and the ring face itself come into one plane. Thus, when the bladed ring is inserted in the groove of the turbine drum or casing f the blade roots Z) are brought to bear against the side wall of the groove in the turbine. I have also illustrated in Fig. 13 a small space 0 below the holding ring n. This is for the purpose of insuring a tight side holding of the blades. In Fig. 13 this space 0 is somewhat exaggerated. It will be understood that in all cases described such a space is preferably left, but in the forms illustrated this space is not so clearly shown, as it is so extremely small when the ring is calked into place.

Instead of arranging the blades to press against the side wall of the groove in the turbine drum or casing, I may arrange these roots to press against the calking ring 9 as illustrated in Figs. 15 and 16. In these figures the blade has been omitted and Fig. 15 shows the relationship of the parts before calking. After calking the projecting tooth parts 29 of the holding ring n are caused to tighten down on the blade root and foot and the calking ring g bears tightly against the right hand face of the holding ring 1?. in Figs. 14 and 15.

It will be seen that in all the forms illustrated the cross section of the blade root in plan is bounded by a straight line figure. In this way the grooves of the holding ring may be made to exactly fit the turbine blade roots and a better holding action is secured.

I claim 1. A blade fastening for turbines having in combination in the blade-ring carrying groove a blade root and a foot thereon, the blade root throughout its whole depth having a shape in cross section which is bordered by straight lines and of substantially the same area in cross section as the blade itself and the root being connected with the foot in its whole breadth, a holding ring provided with grooves gripping the blade roots and a calking ring for fastening purposes.

2. A blade fastening for turbines having in combination in the blade ring carrying grooves a blade root and a foot thereon, the blade root throughout its whole depth having substantially the same cross section as the blade itself and the root being connected with the foot in its whole breadth, a divided holding ring provided with grooves gripping said blade roots from opposite sides.

3. A blade fastening for turbines having in combination in the blade ring carrying grooves a blade root and a foot thereon extending on both sides of the root, the blade root throughout its whole depth having a shape in cross section which is bordered by straight lines and of substantially the same area in cross section as the blade itself and the root being connected with the foot in its whole breadth, a holding ring provided with grooves gripping said blade roots and a callzing ring for fastening purposes.

at. A blade fastening for turbines having in combination in the blade ring carrying grooves, a blade root and a foot thereon extending on both sides of the root, the blade root throughout its whole depth having substantially the same cross section as the blade itself and the root being connected with the foot in its whole breadth, a divided holding ring provided with grooves gripping the blade roots from opposite sides and a calking ring for fastening purposes.

5. A blade fastening for turbines having in combination in the blade ring carrying grooves, a blade root and a foot thereon, the blade root throughout its whole depth having substantially the same cross section as the blade itself and being provided with a downwardly extending taper and the root being connected with the foot in its whole breadth, a holding ring provided with side grooves engaging the blade roots and a calking ring arranged to press against said holding ring at one side.

(3. A blade fastening for turbines having in combination in the blade ring carrying rooves a blade root and a foot thereon, the

blade root throughout its whole depth having substantially the same cross section as the blade itself and being provided with a downwardly extending taper and the root being connected with the foot in its whole breadth, a holding ring provided with side grooves engaging the blade roots, said holding ring being free from the bottom of the groove in the turbine blade carrying member and a calking ring arranged to press against said holding ring at one side.

In witness whereof I have hereunto set my hand in the presence of two witnesses.

CARL ROTH.

Witnesses E. STRUMSKI, E. FRIESE. 

